shill: Remove IPConfig/DHCPConfig's dependency on Device.

They care about the device name only so use that instead. This eliminates the
need for some circular dependencies.

BUG=chromium-os:16796
TEST=unit tests

Change-Id: Ibfa4eacac2b04b9311abfb76972aaf032c6013aa
Reviewed-on: http://gerrit.chromium.org/gerrit/2943
Reviewed-by: Darin Petkov <petkov@chromium.org>
Tested-by: Darin Petkov <petkov@chromium.org>
diff --git a/dhcp_config.h b/dhcp_config.h
index 16d8442..bf9ff82 100644
--- a/dhcp_config.h
+++ b/dhcp_config.h
@@ -11,7 +11,6 @@
 #include <glib.h>
 #include <gtest/gtest_prod.h>  // for FRIEND_TEST
 
-#include "shill/device.h"
 #include "shill/ipconfig.h"
 
 namespace shill {
@@ -28,7 +27,7 @@
   typedef std::map<std::string, DBus::Variant> Configuration;
 
   DHCPConfig(DHCPProvider *provider,
-             DeviceConstRefPtr device,
+             const std::string &device_name,
              GLibInterface *glib);
   virtual ~DHCPConfig();